This invention relates to a package where a chip module is connected to a printed circuit board (PCB) via a land grid array (LGA), and more particularly, the package includes the LGA on a top surface of the PCB and a power supply connected to the PCB via a second LGA on the bottom surface of the PCB.
One type of surface-mount packaging used for integrated circuits (IC) is pin grid array (PGA). In PGA pins are used to conduct electrical signals from the integrated circuit to a printed circuit board (PCB) the IC is placed on. Another type of surface-mount packaging used for integrated circuits is ball grid array (BGA). Using BGA, connector pins are replaced by balls of solder joined to the bottom of the package. A device is placed on a PCB that carries copper pads in a pattern that matches the solder balls. Repair to the components of the chip module is completed by shipping the PCB and soldered module to a repair facility which is expensive and time consuming.
A land grid array (LGA) is a physical interface for some microprocessors package families. Unlike the pin grid array (PGA) interface found on most available processors, there are no pins on the chip module for LGA. Instead, on the LGA, is a separate, interposed structure consisting of an array of conducting compliant contacts which touch the conductive pads on the bottom of the chip module and also touch the pads on the motherboard.
Land Grid Array (LGA) interposers are typically used to reversibly connect a chip module to a printed circuit board (PCB). This brings both signal and power from the PCB to and from the module. Power supplies serving the module are usually located on the PCB as close to the module as possible to minimize the wiring distance and the associated resistive losses and time delays. However, the minimal distance possible where a power supply is immediately adjacent to the module still limits the closeness to an extent equal to or greater than the width of the power supply for at least some fraction of wiring paths.
Chip packages experience time delays and higher power usage resulting from the distance between the power supply and the module. Current packages attempt to mitigate the delay time resulting from the distance between the power supply and the module by having small decoupling capacitors (decaps) soldered on the printed wiring board, and as close to the module as possible to store as much energy from the power supply. Thus, when the chip calls for power, the power comes from the capacitor first rather than having to go all the way out to a power supply.
Moreover, in conventional electronic packaging designs utilizing BGA connections, repair to chip modules is conducted off-line, e.g. at a repair facility which requires extra cost in terms of shipping, time delays, etc.
It would therefore be desirable for a chip module to be capable of being repaired in the field. It would also be desirable for components of a chip module to be individually removable for repair. It would further be desirable to minimize wiring distances between components and a power supply in a module package.